Members of the Massachusetts delegation will be joined by members of Congress from neighboring states to thank law enforcement officers, medical professionals, first responders, and ordinary citizens for their bravery, dedication, and sacrifice.

The delegation said the first responders saved hundreds of lives in the immediate aftermath of the attack and countless more from the threat of future attacks.

They will also honor those killed — Martin Richard, Krystle Campbell, Lu Lingzi, and Officer Sean Collier — and the more than 200 wounded.